@Gazza Classic case of "hey, this show's still popular after four seasons, we'd better not actually resolve any of the dramatic tension central to its success". Totally contrived.
That's where the most of the best of these drama serials fall over. When they reach popularity they start making lots of creative concessions to the studio's need for them to stay at that level. Things get slow, get bogged down, characters fall into established and boring patterns, stars become jaded and dial it in.
Then if they're lucky, when they go off the boil they get a final season to try to bolt some sort of half-arsed conclusion onto the deflating soufflé, usually with a stack of magical bullshit that insults the show's original premise.
